At the time, the city of Dallas' emergency dispatch system was being clogged with so-called "ghost calls" -- duplicate calls generated from legitimate 911 calls, city officials have said.

The problem went on for months and has been blamed partly on an issue with T-Mobile's network technology. The city's call center staffing was also scrutinized after the incident.

In the lawsuit, the babysitter on that day did reach the boy's mother, Bridget Alex, who raced home and rushed Brandon to the hospital. The baby was transferred to another hospital, where he was pronounced dead.

Bridget is seeking damages and compensation for "mental anguish, loss of consortium, grief, bereavement, loss of future financial contributions, loss of services, loss of advice, care and counsel, loss of society and companionship, medical, funeral, and burial expenses," among other things.

Since Brandon's death, T-Mobile has adjusted its cell phone network to try to solve the 911 problem, and the Dallas emergency call center added operators to relieve the burden of "ghost calls," city officials said.